Omar Al Zabir, from Pageflakes.com, has built a cool prototype using ASP.NET AJAX that implements an 'ajaxified' start page portal site. Cool: Built on ASP.NET AJAX + .NET 3.0 + DLinQ in 7 days! Not as cool... it mimics Google. :) Although, he also has the Windows Live banner at the top?!
Check out the full article + source code that he has posted up on The Code Project.